Summaries of exchanges between Sir John Frederick William Herschel and Johann Wilhelm Andreas Pfaff Summaries of exchanges between German mathematician Johann Whilhelm Andreas Pfaff (1774-1835) and Sir John Frederick William Herschel, made by the latter, likely as a calendar of exchanges related to his time as Foreign Secretary to the Astronomical Society. The notes are headed 'Pfaff - Professor of - at Erlangen'. First letter mentioned dated October 20 1823 from Sir John Herschel to Pfaff including a packet of books "in consequence of a application to me on his part by Prof. Schumacher stating" Pfaff's intention to translate the work of Sir William Herschel into German. Promise from Herschel to send a biography written by himself, sends copies of books and essays from Phil. Trans. Second letter is simply mentioned with date [3 July 1824] and place [from Caltaglione in Sicily]. Finally mention of a visit in 1824 at Erlangen "called on him at Erlanger & saw his daughter, he was at Stuttgard" 1823-1824